The present invention relates to a hydraulic automotive vehicle brake system with wheel slip control which includes at least one non-return valve with a valve seat and a closure member that is lifted from the valve seat during evacuation of the brake system.
German patent application No. 43 37 133 discloses a hydraulic automotive vehicle brake system with wheel slip control, wherein in each brake circuit of the anti-lock device and/or traction slip control device at least one non-return valve is used having a valve seat which is not closed by the closure member of the non-return valve upon evacuation of the brake system. The objective of this provision is that the valve seat is not covered before and during filling of the system when the system is unpressurized. Thus, a connection exists between the primary circuit and the secondary circuit by way of the open non-return valve, with the result that the secondary circuit can be evacuated and filled with fluid without the need to actuate the normally closed magnetic valve. In the capacity of a closure member, the non-return valve has a ball without a spring. During pressure increase in the system caused by a braking operation, correspondingly great flow forces must act upon the non-return valve in order that the closure member, configured as a ball, is entrained and urged against the valve seat. In another type of construction of the spherical non-return valve, the ball is pressed against its valve seat by the effect of gravitational force. However, these reflections are mainly theoretical so that it is not precluded in practical operations that the closing movement of the spherical non-return valve, which is to be effected by flow forces or by gravitational force, will reliably be provided. Due to the high sealing requirements placed on the non-return valve (which are comparable with the sealing requirements of a pressure modulation valve inserted in the outlet to the wheel brake and closed in the initial position), an absolutely reliable closure of the non-return valve must be ensured in any case. A leakage-free closing function of metallic spherical closure members is, however, not ensured in the prior art.
Therefore, an object of the present invention is to improve upon a hydraulic automotive vehicle brake system with wheel slip control of the above-mentioned type to such effect that a lowcost, functionally reliable and especially non-leaking non-return valve is provided by simple means which, in case of need, automatically permits self-exhaustion of the low-pressure accumulator and evacuation of the pump suction conduit during the high-vacuum process.